Biomass graded utilization system and method for photo-driven nitrogen cycle pyrolysis-gasification

Abstract

The invention discloses a light-driven nitrogen cycle pyrolysis-gasification biomass graded utilization system and method, and relates to the technical field of biomass graded utilization, the system comprises a pretreatment unit, a light-driven nitrogen-doped pyrolysis reactor and a photocatalytic nitrogen de-intercalation gasification reactor as core parts, an energy collection unit and a post-treatment unit. The method comprises condensation ammonia-doped pyrolysis and condensation gasification: pretreated biomass is subjected to condensation ammonia-doped pyrolysis in a pyrolysis section to generate high-activity nitrogen-doped coke and hydrogen, then the nitrogen-doped coke enters a gasification section to be subjected to condensation gasification, under the action of high-concentration water vapor, nitrogen elements in the coke are deintercalated, more active sites are released, NH3 is generated at the same time, and the nitrogen-doped coke enters the gasification section to be subjected to condensation gasification; the nitrogen can flow back to the pyrolysis zone for cyclic utilization, and a nitrogen doping-de-intercalation catalytic cycle process is formed. The light-driven nitrogen cycle grading technology is adopted, efficient doping of nitrogen elements at the high temperature is achieved, high-activity nitrogen-doped coke is generated, and production of high-quality synthesis gas and cyclic utilization of nitrogen are achieved.

Description

Technical Field

[0001] This invention relates to the field of biomass grading and utilization technology, and in particular provides a biomass grading and utilization system and method driven by nitrogen cycle pyrolysis-gasification. Background Technology Biomass refers to organic matter derived from organisms such as plants, animals, and microorganisms, including renewable resources such as agricultural and forestry waste, energy crops, algae, and organic waste. As an important component of renewable energy, the efficient conversion and utilization of biomass energy is of great significance for optimizing the energy structure.

[0002] Currently, traditional biomass gasification technologies mostly rely on high-temperature thermochemical processes (reaction temperatures > 1000℃), which suffer from problems such as high reaction energy consumption, low gasification efficiency, and poor syngas quality. While conventional pyrolysis-gasification staged treatment methods can improve product quality to some extent, they lack efficient energy input and catalytic systems, failing to fully break down the complex molecular structure of biomass. This results in persistently high reaction activation energies, limiting the improvement of biomass conversion efficiency.

[0003] Meanwhile, the role of nitrogen in fuel conversion has not been fully explored, and conventional technologies struggle to achieve efficient nitrogen recycling, leading to resource waste and potential nitrogen pollution risks. For example, in the field of ammonia-blended coal combustion, patent CN 120120555 A discloses a high-temperature, strong-reduction ammonia-blended combustion system and method for coal-fired boilers, coupling oxygen-enriched combustion with air staging technology to improve the ignition conditions and combustion temperature of ammonia through secondary air oxygenation; patent CN 119573044 A discloses a circulating fluidized bed boiler and ammonia-blended combustion method, which decomposes nitrous oxide by precisely controlling the temperature of a cyclone separator and adjusting the ammonia injection amount in real time to treat nitrogen oxides; and patent CN 120292502 A discloses an oxygen-carrier-enhanced circulating fluidized bed boiler ammonia-blended carbon-reducing combustion system and method, which improves the oxygen distribution in the furnace and increases the ammonia-coal combustion efficiency by adding an oxygen carrier to the circulating fluidized bed boiler. All of the above technical solutions use ammonia, air and fuel to burn together. This not only poses a safety hazard that ammonia is prone to ignition and explosion when it comes into contact with oxygen, but also results in insufficient interaction between nitrogen and fuel. Ammonia mainly has a synergistic effect with coal in the physics of combustion, making it difficult to achieve efficient recycling of nitrogen. Summary of the Invention The purpose of this invention is to overcome the shortcomings of traditional biomass conversion technologies, such as high energy consumption, low efficiency, and insufficient utilization of nitrogen resources. It proposes a light-driven nitrogen cycle pyrolysis-gasification biomass graded utilization system and method, which deeply couples light drive with nitrogen cycle to improve the overall gasification efficiency of biomass, produce high-quality syngas and realize the recycling of ammonia, and achieve the mild and efficient conversion of biomass fuel under solar energy drive.

[0004] Therefore, the present invention provides the following technical solution: On one hand, the present invention provides a light-driven nitrogen cycle pyrolysis-gasification biomass staged utilization system, comprising: Pretreatment Unit A: includes a crushing unit, a drying unit, and a screening unit; the crushing unit reduces the particle size of biomass raw materials through mechanical crushing; the crushed biomass enters the drying unit for drying; the dried biomass enters the screening unit to screen the particle size of the material, unqualified particles are returned to the crushing unit for secondary processing, and qualified biomass particles enter the subsequent reaction unit for reaction; Energy harvesting unit B: Heliostat field; The heliostat field reflects sunlight through a certain number of mirror arrays to collect solar energy and convert the collected solar energy into heat energy. It is connected to the pyrolysis reactor and the gasification reactor to provide photothermal and concentrated light drive for the pyrolysis reactor and the gasification reactor, regulate the molecular structure of nitrogen-doped coke and reduce the activation energy of the reaction. Reaction Unit C: a pyrolysis reactor and a gasification reactor; both reactors are equipped with a solar concentrator system to receive solar energy reflected from a heliostat field; the pyrolysis reactor is configured to introduce ammonia gas during the anoxic pyrolysis stage, enabling the biomass feedstock to complete a concentrated ammonia-doped pyrolysis reaction to generate nitrogen-doped coke and hydrogen; the gasification reactor is configured to enable the nitrogen-doped coke to complete a concentrated gasification reaction in a water vapor atmosphere to generate syngas; Post-treatment unit D: condensation and filtration unit, ammonia absorption-desorption tower and gas purification unit; the condensation and filtration unit is used to condense the tar generated by the reaction and filter solid impurities, the ammonia absorption-desorption tower is used to separate, recover and recycle ammonia, and the remaining gas after condensation and separation is converted into usable fuel gas through the gas purification unit.

[0005] Furthermore, the pyrolysis reactor is a screw variable pitch pyrolysis reactor with a long pitch-short pitch distribution along the axial direction; the gasification reactor is a fluidized bed gasification reactor, with the gasifying agent introduced from the bottom of the bed, and the nitrogen-doped coke being transported to the fluidized bed gasification reactor after separation in the transition section of the screw variable pitch pyrolysis reactor; a concentrating receiving system is respectively set above the main pyrolysis reaction section and the fluidized bed, and the pyrolysis coke is separated in the transition section and then enters the fluidized bed gasification reactor for concentrated gasification.

[0006] Furthermore, the pyrolysis reactor and the gasification reactor adopt a coaxial fluidized bed reactor, with the pyrolysis section and the gasification section vertically graded and separated by a distribution plate to achieve temperature gradient control at different stages; ammonia and water vapor distribution plates are respectively installed at the bottom of the pyrolysis section and the gasification section, and a concentrating receiving system is installed on the right side; an overflow pipe is installed on the left side of the pyrolysis section to enter the gasification section, and the pyrolysis coke enters the gasification section for gasification through the overflow pipe. An ash discharge valve is installed below the gasification section to discharge ash. The pyrolysis gas and the gasification gas are merged through pipelines and then enter the post-treatment unit for separation and purification.

[0007] Furthermore, the pyrolysis reactor and the gasification reactor adopt a dual-circulation fluidized bed reaction system. The pyrolysis furnace and the gasification furnace are placed horizontally. A biomass inlet is set at the bottom left side of the pyrolysis furnace, and an ash discharge port is set at the bottom right side of the gasification furnace. Ammonia and water vapor air distribution plates are respectively set at the bottom of the pyrolysis furnace and the gasification furnace, and a focusing window is set on the side wall to focus the reaction zone. Two cyclone separators are connected to the top of the pyrolysis furnace and the gasification furnace for gas-solid separation. Solid nitrogen-doped coke enters the gasification furnace for gasification through the cyclone separator pipeline. The bed material of the two furnaces also circulates bidirectionally through the cyclone separator to realize heat transfer and maintain the fluidized state. The pyrolysis gas and gasification gas generated by the reaction enter the post-treatment unit for separation and purification.

[0008] Furthermore, the reaction temperature in the pyrolysis reactor is 300℃-500℃, and the reaction temperature in the gasification reactor is 500℃-1000℃.

[0009] In another aspect, the present invention also provides a method for graded utilization of biomass using light-driven nitrogen cycle pyrolysis-gasification, which utilizes the above-mentioned light-driven nitrogen cycle pyrolysis-gasification biomass graded utilization system, including: a concentrated ammonia pyrolysis stage and a concentrated gasification stage. Ammonia-doped pyrolysis stage: Pretreated biomass enters the pyrolysis reactor and undergoes anoxic co-pyrolysis with ammonia at a temperature of 300℃-500℃; Under the photothermal drive provided by the heliostat field, the biomass is photo-mediated to achieve directional nitrogen doping, generating highly active nitrogen-doped char with different structures and pyrolysis gas containing H2; The pyrolysis gas and the syngas generated in the subsequent gasification stage are merged and then enter the post-treatment unit D for unified processing; Concentrated gasification stage: Nitrogen-doped coke generated by pyrolysis enters the gasification reactor and undergoes concentrated gasification reaction at 500℃-1000℃ with water vapor as the gasification agent. The high concentration of water further promotes the conversion of coke nitrogen into ammonia. The syngas generated by gasification and the aforementioned pyrolysis gas are condensed and filtered to obtain a mixed gas. The mixed gas is separated and desorbed by an ammonia absorption-desorption tower to generate high-concentration ammonia for recycling. The remaining gas is treated by a gas purification unit to obtain usable fuel gas.

[0010] Furthermore, the reaction gas in the concentrated ammonia pyrolysis stage is ammonia; the gasifying agent in the concentrated gasification stage is water vapor.

[0011] Furthermore, in the pyrolysis section, ammonia is photo-directedly mediated to dope nitrogen into biomass, generating highly active nitrogen-doped coke with different structures. Subsequently, the nitrogen-doped coke undergoes self-photocatalytic gasification under steam conditions to generate syngas. Ammonia is then absorbed and separated in an ammonia absorption-desorption tower to generate high-concentration ammonia water, which is returned to the pyrolyzer for recycling, forming a nitrogen doping-deintercalation catalytic cycle process. The self-photocatalysis refers to the photocatalytic properties generated by the coke's own conjugated orbitals, catalyzing the coke's own cracking and gasification process.

[0012] Compared with existing technologies, this invention achieves the following technical advantages: It utilizes a heliostat field to collect solar energy to drive the reaction, significantly reducing the activation energy. Photogenerated carriers promote the nitrogen doping process, forming highly active nitrogen-doped coke and usable H2 during pyrolysis. The introduction of nitrogen generates different CN conjugated structures, enhancing the photocatalytic process of the coke. Nitrogen deintercalation during gasification releases more active sites. The catalytic-like cycle of pyrolysis nitrogen doping and gasification nitrogen deintercalation significantly improves the overall biomass gasification efficiency. The NH3 generated during subsequent gasification is separated and desorbed by an ammonia absorption-desorption tower and then returned to the pyrolysis reactor, achieving the production of high-quality syngas and the recycling of nitrogen. Compared to the shortcomings of traditional one-pot ammonia-doped gasification, which is prone to combustion explosions and insufficient nitrogen interaction, this invention employs a photo-driven nitrogen cycle staged technology to achieve efficient nitrogen doping at high temperatures and generate highly active nitrogen-doped coke. The catalytic-like cycle of pyrolysis nitrogen doping and gasification nitrogen deintercalation significantly improves the overall biomass gasification efficiency. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a flowchart of the biomass graded utilization process driven by nitrogen cycle pyrolysis-gasification in an embodiment of the present invention; Figure 2 This is a schematic diagram of a biomass grading and utilization device with light-driven nitrogen cycle pyrolysis-gasification in an embodiment of the present invention; Figure 3 This is a schematic diagram of another biomass grading and utilization device driven by nitrogen cycle pyrolysis-gasification in an embodiment of the present invention; Figure 4 This is a schematic diagram of another biomass grading and utilization device driven by nitrogen cycle pyrolysis-gasification in an embodiment of the present invention; Figure 5 The images shown are in-situ infrared spectra of cellulose without ammonia / with ammonia pyrolysis in embodiments of the present invention. Figure 6 Thermogravimetric curves of cellulose coke and ammonia-doped cellulose coke in the embodiments of the present invention are shown. Figure 7 This is a thermogravimetric curve of ammonia-doped cellulose coke under light / non-light conditions in an embodiment of the present invention. Detailed Implementation

[0015] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0016] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0017] This invention utilizes a light-driven nitrogen cycle pyrolysis-gasification biomass staged conversion technology for efficient biomass conversion. In the pyrolysis stage, concentrated ammonia doping is performed, which not only lowers the activation energy of the reaction but also achieves full interaction between nitrogen and fuel, generating highly active nitrogen-doped coke and H2. Subsequently, the nitrogen-doped coke undergoes concentrated gasification under steam conditions, releasing more active sites and generating NH3. After separation, the NH3 can be recycled back to the pyrolysis zone. This invention deeply couples light-driven processes with nitrogen cycling; the "nitrogen doping-deintercalation" process significantly improves biomass gasification efficiency, achieving efficient conversion of biomass under mild conditions. This is a promising method for staged biomass conversion.

[0018] like Figure 1 The aforementioned biomass graded utilization system driven by nitrogen cycle pyrolysis-gasification comprises several units, namely: pretreatment unit A, energy harvesting unit B, reaction unit C, and posttreatment unit D.

[0019] Pretreatment unit A includes a crushing unit 1, a drying unit 2, and a screening unit 3. Crushing unit 1 reduces the particle size of biomass raw materials through mechanical crushing, increasing the specific surface area and improving subsequent reaction efficiency and material flowability. Specifically, crushing unit 1 is equipped with a twin-shaft shear crusher or a hammer mill to crush the biomass raw materials to a particle size of less than 10mm. The dust generated during crushing is purified by a bag filter. The crushed biomass enters drying unit 2 for drying to a moisture content of 20%~25%. This aims to reduce the moisture content of the biomass raw materials, reduce energy consumption in subsequent processes such as pyrolysis, and avoid equipment corrosion and product contamination. The dried biomass enters screening unit 3 for precise particle size screening. The screen apertures are set to 2mm, 5mm, and 8mm, separating the material into three categories: fine powder, qualified particles, and coarse particles. The fine powder and qualified particles enter reaction unit C for reaction, while the coarse particles are returned to crushing unit 1 for secondary crushing. Energy harvesting unit B includes a heliostat field 4. The heliostat field 4 reflects sunlight through an array of mirrors, primarily to collect the solar energy required for the reaction and convert it into heat energy, providing photothermal and concentrated light drive for the reactors in the reaction unit. In practice, the heliostat field 4 is installed in an open area. The mirror array adopts a parabolic design, and the mirror angles are adjusted by a computer control system to ensure that solar energy is precisely focused onto the concentrating receiving surfaces of the pyrolysis reactor 5 and the gasification reactor 6. Insulated pipes are installed between the heliostat field 4 and the reactors to reduce heat transfer losses. Utilizing the heliostat field 4 to collect solar energy lowers the activation energy of the pyrolysis and gasification reactions, allowing the reactions to proceed at a milder temperature. Simultaneously, light can promote nitrogen doping. Photogenerated electrons and holes promote the selective binding of CN bonds in different hybridization states, possessing the potential for the directional synthesis of coke nitrogen with different structures. Through light-mediated directional nitrogen doping, the electronic structure and surface properties of biomass pyrolysis carbon are altered, enhancing the reactivity of the pyrolysis carbon.

[0020] Reaction unit C includes a pyrolysis reactor 5 and a gasification reactor 6. Ammonia gas is introduced into the feed inlet of pyrolysis reactor 5, and a gas flow meter and pressure sensor are installed to control the ammonia flow rate and inlet pressure. Ammonia gas is introduced during the anoxic pyrolysis stage, enabling the biomass feedstock to complete the concentrated ammonia-doped pyrolysis reaction, producing nitrogen-doped coke and hydrogen. A steam inlet is provided in the gasification zone, and the gasification reactor is configured to allow the nitrogen-doped coke to undergo a concentrated gasification reaction in a steam atmosphere, generating syngas. Both the pyrolysis and gasification zones are equipped with photodetectors to receive solar energy reflected from the heliostat field 4. The syngas produced by the pyrolysis and gasification reactions is collected and transported to the post-processing unit D for subsequent treatment processes such as condensation, filtration, separation, and purification. The reaction temperature in pyrolysis reactor 5 is 300℃-500℃, and the reaction temperature in gasification reactor 6 is 500℃-1000℃. The reaction gas in the concentrated ammonia-doped pyrolysis process is ammonia gas. The gasifying agent in the concentrated gasification stage is steam.

[0021] In the pyrolysis section, ammonia is photo-directed to induce nitrogen doping into biomass, generating highly active nitrogen-doped coke with different structures. Subsequently, the nitrogen-doped coke undergoes photocatalytic gasification under steam conditions to generate syngas. Ammonia is then absorbed and separated in ammonia desorption tower 8 to generate high-concentration ammonia water, which is returned to the pyrolyzer for recycling, forming a "nitrogen doping-deintercalation" type catalytic cycle process. Photocatalysis refers to the photocatalytic properties generated by the coke's own conjugated orbitals, catalyzing the coke's own cracking and gasification process.

[0022] The post-treatment unit D consists of a condensation and filtration unit 7, an ammonia absorption-desorption tower 8, and a gas purification unit 9. The condensation and filtration unit 7 condenses the tar generated in the reaction and filters solid impurities. It employs a multi-stage condensation device, sequentially incorporating water cooling and liquid nitrogen condensation stages to condense and separate the tar from the pyrolysis gas and gasification gas, while removing solid impurities through filtration. The ammonia absorption-desorption tower 8 separates, recovers, and recycles ammonia. It uses a packed tower structure filled with high-efficiency ammonia absorption packing material, with H2SO4 solution as the absorbent. High-efficiency ammonia absorption is achieved by adjusting the absorbent flow rate and temperature. The desorption stage uses steam heating to desorb the absorbed ammonia into a high-concentration gas. The remaining gas after condensation and separation is converted into usable fuel gas via the gas purification unit 9. The gas purification unit 9 is equipped with desulfurization, decarbonization, and dust removal equipment, employing activated carbon adsorption, chemical absorption, and other processes to purify the remaining gas into a product that meets fuel gas standards.

[0023] The above-mentioned reaction unit C has multiple implementation methods.

[0024] Specific Implementation Plan 1: (e.g.) Figure 2 As shown, the core of this embodiment involves a variable-pitch screw pyrolyzer and a concentrating fluidized bed gasification reactor operating in series. Both reactors are equipped with concentrating systems to collect sunlight. The variable-pitch screw pyrolyzer replaces the traditional pyrolysis reactor, and the reactor interior employs a long-pitch-short-pitch distribution along the axial direction to precisely control the transport speed of biomass within the pyrolyzer. Subsequently, the pyrolysis char is separated in a transition section and enters the fluidized bed gasification reactor for concentrated gasification.

[0025] Biomass is fed into the pyrolyzer from the left inlet, while NH3, precisely regulated by a gas flow meter and pressure sensor, is introduced from the right inlet. The screw employs a long-pitch pre-feeding section and a short-pitch main reaction section design, coupled with a rotation speed of 10-20 r / min. The reduced pitch extends the residence time of biomass in the main pyrolysis zone, ensuring complete reaction. A concentrating lens above the pyrolysis zone focuses sunlight to form a photothermal field, driving the co-pyrolysis of biomass and NH3. The generated nitrogen-doped coke and pyrolysis gas undergo gas-solid separation in an intermediate transition section. The pyrolysis gas is temporarily collected, while the nitrogen-doped coke enters the concentrated fluidized bed gasification reactor for further reaction. A concentrating lens above the gasification reactor synchronously captures light for energy. The reactor is filled with 0.2-0.8 mm diameter quartz sand as bed material to maintain fluidization. H2O(g) is introduced at the bottom as a gasifying agent, and a gasification gas outlet is located on the right side. Finally, the gasification gas and pyrolysis gas produced by the gasification reaction converge and are transported to the post-processing unit.

[0026] Implementation Scheme 1 employs a series design to achieve precise segmented control of the pyrolysis and gasification processes. Its core advantages lie in the dual optimization of reaction efficiency and material management. The variable-pitch screw pyrolyzer, through the axial distribution of a long-pitch pre-feeding section and a short-pitch main reaction section, coupled with a precise rotation speed of 10-20 r / min, extends the residence time of biomass in the main pyrolysis zone. This ensures sufficient co-pyrolysis of biomass and ammonia under a 300℃-500℃ photothermal field, improving the generation efficiency and activity of nitrogen-doped coke. The transition section's gas-solid separation design rapidly separates nitrogen-doped coke from pyrolysis gas, preventing interference from pyrolysis gas to subsequent gasification reactions. Simultaneously, the gasification reactor adopts a focused fluidized bed structure, internally filled with quartz sand to maintain stable fluidization. Water vapor is introduced at the bottom as a gasifying agent, while a focusing lens above provides synchronous energy, ensuring a stable gasification temperature of 500℃-1000℃ and promoting the efficient conversion of nitrogen-doped coke into syngas. The overall process is tightly integrated, and the variable pitch design extends the material residence time, resulting in high material transfer and energy utilization efficiency. It is suitable for scenarios with high requirements for the precision of reaction process control and small to medium-scale applications.

[0027] Specific Implementation Plan Two: (e.g.) Figure 3 As shown, the core component of this embodiment employs a coaxial fluidized bed reactor, with the pyrolysis and gasification sections vertically separated. While sharing a shell, they are divided by internal structures to achieve temperature gradient control at different stages. Ammonia and water vapor distribution plates are installed at the bottom of the pyrolysis and gasification sections, respectively, to transport the reaction gases. A concentrating solar receiver system is located on the right side to receive sunlight. An overflow pipe is located on the left side of the pyrolysis section, leading into the gasification section. Pyrolysis coke enters the gasification section for gasification via the overflow pipe. An ash discharge valve is located below the gasification section to discharge ash. The pyrolysis gas and gasification gas converge through pipelines and then enter the post-processing stage.

[0028] Pretreated biomass is quantitatively fed into the pyrolysis section through the top feeding port. High-purity NH3 is introduced into the porous ceramic distribution plate at the bottom of the pyrolysis section, driving the biomass into a stirred fluidized state at an apparent gas velocity of 0.5~1.0 m / s. The pyrolysis temperature of the pyrolysis section is maintained at 300~500℃ in conjunction with the solar concentrating system on the right side. The pyrolysis gas is drawn out from the upper left side. Nitrogen-doped coke and tar fall into the gasification section after a residence time of 10~20 minutes controlled by the overflow pipe throttle valve. Saturated water vapor at 150℃ is introduced into the metal distribution plate at the bottom of the gasification section, driving the nitrogen-doped coke into a fluidized state at an apparent gas velocity of 1.0~1.5 m / s. The high temperature of 500~1000℃ is maintained by the continuous heating of the solar concentrating system and the exothermic gasification reaction, achieving deep cracking of tar and complete gasification of nitrogen-doped coke. The gasification gas is drawn out from the middle left side. The gasification gas and pyrolysis gas are merged and transported to the post-processing unit for processing. Ash is periodically discharged every 2~4 hours through the pneumatic ash discharge valve at the bottom. Implementation Scheme 2, with its vertically graded structure, offers significant advantages in space utilization and temperature gradient control. The coaxial upper and lower sections share a common shell, with a central distribution plate separating the pyrolysis and gasification sections, greatly saving equipment floor space and reducing overall system complexity. The pyrolysis and gasification sections are equipped with independent gas distribution and focusing systems, enabling precise and independent control of the reaction temperatures (300-500℃ for pyrolysis and 500-1000℃ for gasification) and atmosphere in both sections, thus meeting their different thermodynamic requirements. Nitrogen-doped coke and tar produced in the pyrolysis section are automatically transported by gravity overflow, eliminating the need for complex external conveying equipment. Furthermore, pyrolysis gas and gasification gas are directly merged into the post-treatment system via pipelines, reducing gas transmission losses. The overall system is compact and easy to operate, saving floor space and achieving temperature gradient control at different stages through its shared shell and internal partitioning. It is suitable for medium-sized applications with limited space and a need for simplified processes.

[0029] Specific Implementation Plan Three: (e.g.) Figure 4 As shown, the core component of this embodiment employs a dual-circulation fluidized bed reaction system. The pyrolysis furnace and gasification furnace are placed horizontally. A biomass inlet is located at the bottom left side of the pyrolysis furnace, and an ash discharge port is located at the bottom right side of the gasification furnace. Air inlets for NH3 and H2O(g) are respectively installed at the bottom of the pyrolysis furnace and gasification furnace. A concentrating window is installed on the side wall to focus the reaction zone. Sunlight inside the pyrolysis furnace is focused through the concentrating window, and combined with the waste heat from the circulating bed material in the gasification furnace, the reaction zone is heated to the pyrolysis temperature. Two cyclone separators are connected to the top of the pyrolysis furnace and gasification furnace for gas-solid separation. Solid nitrogen-doped coke enters the gasification furnace for gasification through the cyclone separator pipeline, and the bed materials from both furnaces also circulate bidirectionally through the cyclone separators, achieving heat transfer and maintaining a fluidized state. The pyrolysis gas and gasification gas generated by the reaction enter a post-treatment unit for separation and purification.

[0030] Biomass undergoes pyrolysis in an NH3 atmosphere, releasing volatiles to form pyrolysis gas. Solid char residue is doped with nitrogen by ammonia, forming nitrogen-doped coke. The pyrolysis gas, carrying the nitrogen-doped coke and bed material, enters cyclone separator A. After separation, the solid nitrogen-doped coke and bed material are fed into the gasifier via the cyclone separator pipeline. In the gasifier, sunlight is focused through a concentrator window, and combined with the waste heat from the bed material, the reaction zone is heated to the gasification temperature. The nitrogen-doped coke reacts with water vapor to generate gasification gas. The gasification gas, carrying the bed material and ash, enters cyclone separator B. After separation, the high-temperature bed material is circulated back to the pyrolysis furnace via pipeline. The bed material from both furnaces circulates bidirectionally through the cyclone separator, achieving heat transfer and maintaining a fluidized state. The pyrolysis gas and gasification gas generated from the reaction enter the post-treatment unit for separation and purification.

[0031] Implementation Scheme 3 employs a horizontally placed dual-furnace design with bidirectional bed material circulation to achieve efficient recycling of energy and materials. Its core advantages lie in enhanced heat recovery and reaction stability. The pyrolysis furnace and gasification furnace are horizontally distributed, with gas-solid separation and bed material circulation achieved through two cyclone separators: the high-temperature bed material from the gasification furnace is separated by cyclone separator B and returned to the pyrolysis furnace, transferring the waste heat generated by the gasification reaction to the pyrolysis section. This assists the solar concentrator system in maintaining the pyrolysis temperature, reducing solar energy consumption and improving energy utilization efficiency. Simultaneously, the nitrogen-doped coke generated in the pyrolysis furnace is separated by cyclone separator A and precisely fed into the gasification furnace. The bidirectional flow of bed material in both furnaces maintains a stable fluidized state and balances the temperature field within the furnace, preventing localized temperature fluctuations from affecting the reaction. Furthermore, the air distribution design, with ammonia introduced into the pyrolysis furnace and water vapor introduced into the gasification furnace, combined with the side-wall concentrator windows focusing the reaction zone, ensures that the two reactions proceed under suitable atmosphere and temperature. The overall system reduces energy waste and improves reaction stability through a circulation mechanism, making it suitable for large-scale application scenarios that require high energy recovery efficiency and pursue long-term continuous operation.

[0032] The biomass grading utilization system using the light-driven nitrogen cycle pyrolysis-gasification in the above embodiments includes two stages: concentrated ammonia pyrolysis and concentrated gasification.

[0033] Ammonia-doped pyrolysis stage: Pretreated biomass is transported to pyrolysis reactor 5. Under photothermal drive provided by heliostat field 4, the temperature of pyrolysis reactor 5 is stably maintained at 300-500℃. Ammonia gas is introduced into pyrolysis reactor 5, where it undergoes co-pyrolysis with the biomass in an oxygen-deficient environment. Under photo-mediated action, the biomass achieves directional nitrogen doping, generating highly reactive nitrogen-doped char and hydrogen. The pyrolysis gas is discharged from the outlet of pyrolysis reactor 5, flows through a pipeline, merges with the syngas generated during the gasification process, and enters the condensation and filtration unit 7.

[0034] Concentrated gasification stage: Nitrogen-doped coke generated from pyrolysis enters gasification reactor 6 through the outlet of pyrolysis reactor 5. Inside the gasification reactor, at a high temperature of 500-1000℃, water vapor acts as a gasifying agent, reacting with the nitrogen-doped coke in a concentrated gasification reaction. During the reaction, high-concentration water promotes the conversion of coke nitrogen into NH3, while simultaneously generating syngas mainly composed of H2 and CH4. The reaction products and pyrolysis gas then enter condensation and filtration unit 7. After tar and solid impurities are removed by the condensation and filtration unit, the mixed gas enters ammonia absorption-desorption tower 8. Inside the ammonia absorption-desorption tower 8, ammonia is effectively separated and recovered, forming high-concentration ammonia gas which is then recycled back to pyrolysis reactor 5. The remaining gas enters gas purification unit 9, where it undergoes desulfurization, denitrification, and decarbonization treatment to obtain usable fuel gas.

[0035] Because of the numerous conjugated structures in the microstructure of coke, these structures generate photogenerated electron-hole pairs under light irradiation, causing C / C bonds to break down and form highly active carbon chain structures with significant photocatalytic activity, thereby promoting the self-photocatalytic gasification reaction. Nitrogen doping, forming CN conjugated structures, further enhances the self-photocatalytic properties of coke. When nitrogen exists in the form of pyridine nitrogen, pyrrole nitrogen, or graphitic nitrogen, it introduces localized electron cloud distortion into the carbon conjugated system, reducing the material's band gap and enhancing its absorption of visible light, thus regulating light absorption efficiency. Simultaneously, the carbon-nitrogen conjugated structure facilitates the separation of photogenerated carriers. Studies have shown that the carrier lifetime of nitrogen-doped carbon materials can be extended by 2-3 times. More active sites are released during gasification, further strengthening the self-photocatalytic gasification process of coke.

[0036] The ammonia gas generated during nitrogen deintercalation in the gasification stage is efficiently separated and desorbed by an ammonia absorption-desorption tower, transforming it into high-concentration ammonia gas, which is then recirculated back to the pyrolysis zone to participate in the reaction, thus establishing a closed-loop ammonia gas recycling system. Relying on mature ammonia separation technology, efficient recycling of nitrogen resources is achieved.

[0037] The following examples illustrate the specific operating conditions and advantages of this invention using cellulose as a biomass carbon source for concentrated ammonia pyrolysis and concentrated gasification, further explained with reference to the accompanying drawings and data. Figure 5 The image shows in-situ infrared data of cellulose pyrolysis with and without ammonia doping. The data shows that, with increasing temperature, the undoped cellulose at 1450 cm⁻¹... -1 Up to 1600cm -1 The complex peak packet corresponds to the formation of C=C and CC in the SP2 / SP3 hybridization during pyrolysis, at 1650 cm⁻¹. -1 Up to 1770cm -1 The peak corresponds to the carbonyl C=O bond, and the C=O peak increases rapidly during the main pyrolysis stage. In contrast, in-situ infrared data from the pyrolysis of ammonia-doped cellulose shows a peak at 1550 cm⁻¹. -1 -1600cm -1The nearby CN and C=C peaks increase rapidly, while the 1650 cm⁻¹ peak... -1 Up to 1770cm -1 The C=O peak was significantly lower than that without ammonia doping. This phenomenon directly proves that nitrogen doping enters the carbon framework, replacing the O functional groups and causing some C=O bonds to break and form CN bonds. The addition of ammonia in cellulose pyrolysis alters the pyrolysis reaction pathway, generating more active nitrogen-doped coke, demonstrating the doping effect of nitrogen in the pyrolysis process.

[0038] Subsequently, the nitrogen-doped coke undergoes a gasification reaction in a water vapor atmosphere. Figure 6 The thermogravimetric curves for the gasification of cellulose coke and ammonia-doped cellulose coke are shown in the figure. The valley temperature of cellulose coke is 770.4℃, while that of ammonia-doped cellulose coke is 737.2℃. The maximum weight loss rate of ammonia-doped cellulose coke is significantly higher than that of undoped cellulose coke. Furthermore, the main gasification reaction temperature of ammonia-doped cellulose coke is earlier and more complete than that of undoped cellulose coke. The promoting effect of light on gasification is... Figure 7 The diagram shows that, compared to not irradiating, the ammonia-doped cellulose coke with added light has a earlier gasification temperature, a faster weight loss rate, and a higher gasification efficiency.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biomass tiered utilization system for light-driven nitrogen cycle pyrolysis-gasification, characterized in that, include: Pretreatment unit A: crushing unit (1), drying unit (2) and screening unit (3); wherein the crushing unit (1) reduces the particle size of biomass raw materials by mechanical crushing; the crushed biomass enters the drying unit (2) for drying; the dried biomass enters the screening unit (3) to screen the particle size of the material, unqualified particles are returned to the crushing unit for secondary processing, and qualified biomass particles enter the subsequent reaction unit for reaction; Energy harvesting unit B: Heliostat field (4); The heliostat field (4) reflects sunlight through a certain number of mirror arrays to collect solar energy and convert the collected solar energy into thermal energy. It is connected to the pyrolysis reactor (5) and the gasification reactor (6) to provide photothermal and concentrated light drive for the pyrolysis reactor (5) and the gasification reactor (5), regulate the molecular structure of nitrogen-doped coke and reduce the activation energy of the reaction. Reaction Unit C: Pyrolysis reactor (5) and gasification reactor (6); both reactors are equipped with a solar concentrator system to receive solar energy reflected by the heliostat field (4); the pyrolysis reactor (5) is configured to introduce ammonia gas during the anoxic pyrolysis stage, so that the biomass raw material completes the concentrated ammonia pyrolysis reaction to generate nitrogen-doped coke and hydrogen gas; the gasification reactor (6) is configured to allow the nitrogen-doped coke to complete the concentrated gasification reaction in a water vapor atmosphere to generate syngas. Post-processing unit D: condensation and filtration unit (7), ammonia absorption-desorption tower (8) and gas purification unit (9); the condensation and filtration unit (7) is used to condense the tar generated by the reaction and filter solid impurities, the ammonia absorption-desorption tower (8) is used to separate, recover and recycle ammonia, and the remaining gas after condensation and separation is converted into usable fuel gas through the gas purification unit (9).

2. The biomass graded utilization system driven by nitrogen cycle pyrolysis-gasification according to claim 1, characterized in that, The pyrolysis reactor (5) is a screw variable pitch pyrolysis reactor with a long pitch-short pitch distribution along the axial direction; the gasification reactor (6) is a fluidized bed gasification reactor, with the gasifying agent introduced from the bottom of the bed, and the nitrogen-doped coke being transported to the fluidized bed gasification reactor after separation by the screw variable pitch pyrolysis reactor through the transition section; a concentrating receiving system is set above the pyrolysis main reaction section and the fluidized bed, and the pyrolysis coke is separated by the transition section and then enters the fluidized bed gasification reactor for concentrated gasification.

3. The biomass graded utilization system driven by nitrogen cycle pyrolysis-gasification according to claim 1, characterized in that, The pyrolysis reactor (5) and the gasification reactor (6) are coaxial fluidized bed reactors. The pyrolysis section and the gasification section are vertically graded and separated by a distribution plate to achieve temperature gradient control at different stages. Ammonia and water vapor distribution plates are respectively installed at the bottom of the pyrolysis section and the gasification section, and a focusing receiving system is installed on the right side. An overflow pipe is installed on the left side of the pyrolysis section to enter the gasification section. The pyrolysis coke enters the gasification section for gasification through the overflow pipe. An ash discharge valve is installed below the gasification section to discharge ash. The pyrolysis gas and the gasification gas are merged through pipelines and then enter the post-treatment unit for separation and purification.

4. The biomass graded utilization system of light-driven nitrogen cycle pyrolysis-gasification according to claim 1, characterized in that, The pyrolysis reactor (5) and gasification reactor (6) adopt a double-circulation fluidized bed reaction system. The pyrolysis furnace and the gasification furnace are placed horizontally. The biomass inlet is set at the bottom left side of the pyrolysis furnace and the ash discharge port is set at the bottom right side of the gasification furnace. Ammonia and water vapor air distribution plates are set at the bottom of the pyrolysis furnace and the gasification furnace respectively. A focusing window is set on the side wall to focus the reaction zone. Two cyclone separators are connected to the top of the pyrolysis furnace and the gasification furnace for gas-solid separation. Solid nitrogen-doped coke enters the gasification furnace for gasification through the cyclone separator pipeline. The bed material of the two furnaces also circulates bidirectionally through the cyclone separator to realize heat transfer and maintain the fluidized state. The pyrolysis gas and gasification gas generated by the reaction enter the post-treatment unit for separation and purification.

5. A biomass tiered utilization system for light-driven nitrogen cycle pyrolysis-gasification according to claim 1, characterized in that, The reaction temperature in the pyrolysis reactor (5) is 300℃-500℃, and the reaction temperature in the gasification reactor (6) is 500℃-1000℃.

6. A method for graded utilization of biomass through light-driven nitrogen cycle pyrolysis-gasification, characterized in that, The application of a biomass graded utilization system with light-driven nitrogen cycle pyrolysis-gasification as described in any one of claims 1 to 5 includes: a concentrated ammonia-doped pyrolysis stage and a concentrated gasification stage; Ammonia-doped pyrolysis stage: The pretreated biomass enters the pyrolysis reactor (5) and undergoes anoxic co-pyrolysis with ammonia at a temperature of 300℃-500℃; Under the photothermal drive provided by the heliostat field (4), the biomass is photo-mediated to achieve directional nitrogen doping, generating highly active nitrogen-doped char with different structures and pyrolysis gas containing H2; The pyrolysis gas and the synthesis gas generated in the subsequent gasification stage are merged and then enter the post-treatment unit D for unified treatment; Concentrated gasification stage: The nitrogen-doped coke generated by pyrolysis enters the gasification reactor (6) and undergoes concentrated gasification reaction under the conditions of 500℃-1000℃ and water vapor as gasification agent. The high concentration of water promotes the conversion of coke nitrogen into ammonia. The syngas generated by gasification and the aforementioned pyrolysis gas are condensed and filtered to obtain a mixed gas. The mixed gas is separated and desorbed by the ammonia absorption-desorption tower (8) to generate high concentration ammonia for recycling. The remaining gas is treated by the gas purification unit (9) to obtain usable fuel gas.

7. A method for graded utilization of biomass through light-driven nitrogen cycle pyrolysis-gasification according to claim 6, characterized in that, The reaction gas in the ammonia-doped pyrolysis stage of the concentrated light is ammonia; the gasifying agent in the concentrated light gasification stage is water vapor.

8. A method for graded utilization of biomass through light-driven nitrogen cycle pyrolysis-gasification according to claim 6, characterized in that, In the pyrolysis section, ammonia is photo-directed to induce nitrogen doping into biomass, which then pyrolyzes to generate highly active nitrogen-doped coke with different structures. Subsequently, the nitrogen-doped coke undergoes photocatalytic gasification under steam conditions to generate syngas. Ammonia is then separated by an ammonia absorption-desorption tower (8) to generate high-concentration ammonia water, which is then recycled back into the pyrolyzer, forming a nitrogen doping-deintercalation catalytic cycle. The self-photocatalysis refers to the photocatalytic properties generated by the coke's own conjugate orbitals, which catalyze the coke's own cracking and gasification process.

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